McEvoy Software Ltd provides its software on a number of licenses to meet the needs of different users.

Free and Open Source for Basic Webdav

Basic webdav funciionality (ie DAV level 1 only) is available in apache licensed software - milton-api and milton-ce. This is suitable for browsing and file uploading for most webdav clients, but should generally not be used if you want broad compatibility across operating systems and office productivity software.